/*
 * drivers/nand/nand_util.c
 *
 * Copyright (C) 2006 by Weiss-Electronic GmbH.
 * All rights reserved.
 *
 * @author: Guido Classen <clagix@gmail.com>
 * @descr:  NAND Flash support
 * @references: borrowed heavily from Linux mtd-utils code:
 *      flash_eraseall.c by Arcom Control System Ltd
 *      nandwrite.c by Steven J. Hill (sjhill@realitydiluted.com)
 *                 and Thomas Gleixner (tglx@linutronix.de)
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 *
 */

#include <common.h>

#if (CONFIG_COMMANDS & CFG_CMD_NAND) && !defined(CFG_NAND_LEGACY)

#include <command.h>
#include <watchdog.h>
#include <malloc.h>

#include <nand.h>
#include <jffs2/jffs2.h>

typedef struct erase_info erase_info_t;
typedef struct mtd_info   mtd_info_t;

/* support only for native endian JFFS2 */
#define cpu_to_je16(x) (x)
#define cpu_to_je32(x) (x)

/*****************************************************************************/
static int nand_block_bad_scrub(struct mtd_info *mtd, loff_t ofs, int getchip)
{
    return 0;
}

/**
 * nand_erase_opts: - erase NAND flash with support for various options
 *            (jffs2 formating)
 *
 * @param meminfo   NAND device to erase
 * @param opts      options,  @see struct nand_erase_options
 * @return      0 in case of success
 *
 * This code is ported from flash_eraseall.c from Linux mtd utils by
 * Arcom Control System Ltd.
 */
int nand_erase_opts(nand_info_t *meminfo, const nand_erase_options_t *opts)
{
    struct jffs2_unknown_node cleanmarker;
    int clmpos = 0;
    int clmlen = 8;
    erase_info_t erase;
    ulong erase_length;
    int isNAND;
    int bbtest = 1;
    int result;
    int percent_complete = -1;
    int (*nand_block_bad_old)(struct mtd_info *, loff_t, int) = NULL;
    const char *mtd_device = meminfo->name;

    memset(&erase, 0, sizeof(erase));

    erase.mtd = meminfo;
    erase.len  = meminfo->erasesize;
    erase.addr = opts->offset;
    erase_length = opts->length;

    isNAND = meminfo->type == MTD_NANDFLASH ? 1 : 0;

    if (opts->jffs2) {
        cleanmarker.magic = cpu_to_je16 (JFFS2_MAGIC_BITMASK);
        cleanmarker.nodetype = cpu_to_je16 (JFFS2_NODETYPE_CLEANMARKER);
        if (isNAND) {
            struct nand_oobinfo *oobinfo = &meminfo->oobinfo;

            /* check for autoplacement */
            if (oobinfo->useecc == MTD_NANDECC_AUTOPLACE) {
                /* get the position of the free bytes */
                if (!oobinfo->oobfree[0][1]) {
                    printf(" Eeep. Autoplacement selected "
                           "and no empty space in oob\n");
                    return -1;
                }
                clmpos = oobinfo->oobfree[0][0];
                clmlen = oobinfo->oobfree[0][1];
                if (clmlen > 8)
                    clmlen = 8;
            } else {
                /* legacy mode */
                switch (meminfo->oobsize) {
                case 8:
                    clmpos = 6;
                    clmlen = 2;
                    break;
                case 16:
                    clmpos = 8;
                    clmlen = 8;
                    break;
                case 64:
                    clmpos = 16;
                    clmlen = 8;
                    break;
                }
            }

            cleanmarker.totlen = cpu_to_je32(8);
        } else {
            cleanmarker.totlen =
                cpu_to_je32(sizeof(struct jffs2_unknown_node));
        }
        cleanmarker.hdr_crc =  cpu_to_je32(
            crc32_no_comp(0, (unsigned char *) &cleanmarker,
                      sizeof(struct jffs2_unknown_node) - 4));
    }

    /* scrub option allows to erase badblock. To prevent internal
     * check from erase() method, set block check method to dummy
     * and disable bad block table while erasing.
     */
    if (opts->scrub) {
        struct nand_chip *priv_nand = meminfo->priv;

        nand_block_bad_old = priv_nand->block_bad;
        priv_nand->block_bad = nand_block_bad_scrub;
        /* we don't need the bad block table anymore...
         * after scrub, there are no bad blocks left!
         */
        if (priv_nand->bbt) {
            kfree(priv_nand->bbt);
        }
        priv_nand->bbt = NULL;
    }

    for (;
         erase.addr < opts->offset + erase_length;
         erase.addr += meminfo->erasesize) {

        WATCHDOG_RESET ();

        if (!opts->scrub && bbtest) {
            int ret = meminfo->block_isbad(meminfo, erase.addr);
            if (ret > 0) {
                if (!opts->quiet)
                    printf("\rSkipping bad block at  "
                           "0x%08x                   "
                           "                         \n",
                           erase.addr);
                continue;

            } else if (ret < 0) {
                printf("\n%s: MTD get bad block failed: %d\n",
                       mtd_device,
                       ret);
                return -1;
            }
        }

        result = meminfo->erase(meminfo, &erase);
        if (result != 0) {
            printf("\n%s: MTD Erase failure: %d\n",
                   mtd_device, result);
            continue;
        }

        /* format for JFFS2 ? */
        if (opts->jffs2) {

            /* write cleanmarker */
            if (isNAND) {
                size_t written;
                result = meminfo->write_oob(meminfo,
                                erase.addr + clmpos,
                                clmlen,
                                &written,
                                (unsigned char *)
                                &cleanmarker);
                if (result != 0) {
                    printf("\n%s: MTD writeoob failure: %d\n",
                           mtd_device, result);
                    continue;
                }
            } else {
                printf("\n%s: this erase routine only supports"
                       " NAND devices!\n",
                       mtd_device);
            }
        }

        if (!opts->quiet) {
            int percent = (int)
                ((unsigned long long)
                 (erase.addr+meminfo->erasesize-opts->offset)
                 * 100 / erase_length);

            /* output progress message only at whole percent
             * steps to reduce the number of messages printed
             * on (slow) serial consoles
             */
            if (percent != percent_complete) {
                percent_complete = percent;

                printf("\rErasing at 0x%x -- %3d%% complete.",
                       erase.addr, percent);

                if (opts->jffs2 && result == 0)
                    printf(" Cleanmarker written at 0x%x.",
                           erase.addr);
            }
        }
    }
    if (!opts->quiet)
        printf("\n");

    if (nand_block_bad_old) {
        struct nand_chip *priv_nand = meminfo->priv;

        priv_nand->block_bad = nand_block_bad_old;
        priv_nand->scan_bbt(meminfo);
    }

    return 0;
}

#define MAX_PAGE_SIZE   2048
#define MAX_OOB_SIZE    64

/*
 * buffer array used for writing data
 */
static unsigned char data_buf[MAX_PAGE_SIZE];
static unsigned char oob_buf[MAX_OOB_SIZE];

/* OOB layouts to pass into the kernel as default */
static struct nand_oobinfo none_oobinfo = {
    .useecc = MTD_NANDECC_OFF,
};

static struct nand_oobinfo jffs2_oobinfo = {
    .useecc = MTD_NANDECC_PLACE,
    .eccbytes = 6,
    .eccpos = { 0, 1, 2, 3, 6, 7 }
};

static struct nand_oobinfo yaffs_oobinfo = {
    .useecc = MTD_NANDECC_PLACE,
    .eccbytes = 6,
    .eccpos = { 8, 9, 10, 13, 14, 15}
};

static struct nand_oobinfo autoplace_oobinfo = {
    .useecc = MTD_NANDECC_AUTOPLACE
};

/**
 * nand_write_opts: - write image to NAND flash with support for various options
 *
 * @param meminfo   NAND device to erase
 * @param opts      write options (@see nand_write_options)
 * @return      0 in case of success
 *
 * This code is ported from nandwrite.c from Linux mtd utils by
 * Steven J. Hill and Thomas Gleixner.
 */
int nand_write_opts(nand_info_t *meminfo, const nand_write_options_t *opts)
{
    int imglen = 0;
    int pagelen;
    int baderaseblock;
    int blockstart = -1;
    loff_t offs;
    int readlen;
    int oobinfochanged = 0;
    int percent_complete = -1;
    struct nand_oobinfo old_oobinfo;
    ulong mtdoffset = opts->offset;
    ulong erasesize_blockalign;
    u_char *buffer = opts->buffer;
    size_t written;
    int result;
    int skipfirstblk = opts->skipfirstblk;

    if (opts->pad && opts->writeoob) {
        printf("Can't pad when oob data is present.\n");
        return -1;
    }

    /* set erasesize to specified number of blocks - to match
     * jffs2 (virtual) block size */
    if (opts->blockalign == 0) {
        erasesize_blockalign = meminfo->erasesize;
    } else {
        erasesize_blockalign = meminfo->erasesize * opts->blockalign;
    }

    /* make sure device page sizes are valid */
    if (!(meminfo->oobsize == 16 && meminfo->oobblock == 512)
        && !(meminfo->oobsize == 8 && meminfo->oobblock == 256)
        && !(meminfo->oobsize == 64 && meminfo->oobblock == 2048)) {
        printf("Unknown flash (not normal NAND)\n");
        return -1;
    }

    /* read the current oob info */
    memcpy(&old_oobinfo, &meminfo->oobinfo, sizeof(old_oobinfo));

    /* write without ecc? */
    if (opts->noecc) {
        memcpy(&meminfo->oobinfo, &none_oobinfo,
               sizeof(meminfo->oobinfo));
        oobinfochanged = 1;
    }

    /* autoplace ECC? */
    if (opts->autoplace && (old_oobinfo.useecc != MTD_NANDECC_AUTOPLACE)) {

        memcpy(&meminfo->oobinfo, &autoplace_oobinfo,
               sizeof(meminfo->oobinfo));
        oobinfochanged = 1;
    }

    /* force OOB layout for jffs2 or yaffs? */
    if (opts->forcejffs2 || opts->forceyaffs) {
        struct nand_oobinfo *oobsel =
            opts->forcejffs2 ? &jffs2_oobinfo : &yaffs_oobinfo;

        if (meminfo->oobsize == 8) {
            if (opts->forceyaffs) {
                printf("YAFSS cannot operate on "
                       "256 Byte page size\n");
                goto restoreoob;
            }
            /* Adjust number of ecc bytes */
            jffs2_oobinfo.eccbytes = 3;
        }

        memcpy(&meminfo->oobinfo, oobsel, sizeof(meminfo->oobinfo));
        oobinfochanged = 1;
    }

    /* get image length */
    imglen = opts->length;
    pagelen = meminfo->oobblock
        + ((opts->writeoob != 0) ? meminfo->oobsize : 0);

    /* check, if file is pagealigned */
    if ((!opts->pad) && ((imglen % pagelen) != 0)) {
        printf("Input block length is not page aligned\n");
        goto restoreoob;
    }

    /* check, if length fits into device */
    if (((imglen / pagelen) * meminfo->oobblock)
         > (meminfo->size - opts->offset)) {
        printf("Image %d bytes, NAND page %d bytes, "
               "OOB area %u bytes, device size %u bytes\n",
               imglen, pagelen, meminfo->oobblock, meminfo->size);
        printf("Input block does not fit into device\n");
        goto restoreoob;
    }

    if (!opts->quiet)
        printf("\n");

    /* get data from input and write to the device */
    while (imglen && (mtdoffset < meminfo->size)) {

        WATCHDOG_RESET ();

        /*
         * new eraseblock, check for bad block(s). Stay in the
         * loop to be sure if the offset changes because of
         * a bad block, that the next block that will be
         * written to is also checked. Thus avoiding errors if
         * the block(s) after the skipped block(s) is also bad
         * (number of blocks depending on the blockalign
         */
        while (blockstart != (mtdoffset & (~erasesize_blockalign+1))) {
            blockstart = mtdoffset & (~erasesize_blockalign+1);
            offs = blockstart;
            baderaseblock = 0;

            /* check all the blocks in an erase block for
             * bad blocks */
            if (!opts->nocheckbadblk) {
                do {
                    int ret = meminfo->block_isbad(meminfo, offs);

                    if (ret < 0) {
                        printf("Bad block check failed\n");
                        goto restoreoob;
                    }
                    if (ret == 1) {
                        baderaseblock = 1;
                        if (!opts->quiet)
                            printf("\rBad block at 0x%lx "
                                   "in erase block from "
                                   "0x%x will be skipped\n",
                                   (long) offs,
                                   blockstart);
                    }

                    if (baderaseblock) {
                        mtdoffset = blockstart
                            + erasesize_blockalign;
                    }
                    offs +=  erasesize_blockalign
                        / opts->blockalign;
                } while (offs < blockstart + erasesize_blockalign);
            }
        }

        /* skip the first good block when wirte yaffs image, by www.embedsky.net */
        if (skipfirstblk) {
            mtdoffset += erasesize_blockalign;
            skipfirstblk = 0;
            continue;
        }

        readlen = meminfo->oobblock;
        if (opts->pad && (imglen < readlen)) {
            readlen = imglen;
            memset(data_buf + readlen, 0xff,
                   meminfo->oobblock - readlen);
        }

        /* read page data from input memory buffer */
        memcpy(data_buf, buffer, readlen);
        buffer += readlen;

        if (opts->writeoob) {
            /* read OOB data from input memory block, exit
             * on failure */
            memcpy(oob_buf, buffer, meminfo->oobsize);
            buffer += meminfo->oobsize;

            /* write OOB data first, as ecc will be placed
             * in there*/
            result = meminfo->write_oob(meminfo,
                            mtdoffset,
                            meminfo->oobsize,
                            &written,
                            (unsigned char *)
                            &oob_buf);

            if (result != 0) {
                printf("\nMTD writeoob failure: %d\n",
                       result);
                goto restoreoob;
            }
            imglen -= meminfo->oobsize;
        }

        /* write out the page data */
        result = meminfo->write(meminfo,
                    mtdoffset,
                    meminfo->oobblock,
                    &written,
                    (unsigned char *) &data_buf);

        if (result != 0) {
            printf("writing NAND page at offset 0x%lx failed\n",
                   mtdoffset);
            goto restoreoob;
        }
        imglen -= readlen;

        if (!opts->quiet) {
            int percent = (int)
                ((unsigned long long)
                 (opts->length-imglen) * 100
                 / opts->length);
            /* output progress message only at whole percent
             * steps to reduce the number of messages printed
             * on (slow) serial consoles
             */
            if (percent != percent_complete) {
                printf("\rWriting data at 0x%x "
                       "-- %3d%% complete.",
                       mtdoffset, percent);
                percent_complete = percent;
            }
        }

        mtdoffset += meminfo->oobblock;
    }

    if (!opts->quiet)
        printf("\n");

restoreoob:
    if (oobinfochanged) {
        memcpy(&meminfo->oobinfo, &old_oobinfo,
               sizeof(meminfo->oobinfo));
    }

    if (imglen > 0) {
        printf("Data did not fit into device, due to bad blocks\n");
        return -1;
    }

    /* return happy */
    return 0;
}

/**
 * nand_read_opts: - read image from NAND flash with support for various options
 *
 * @param meminfo   NAND device to erase
 * @param opts      read options (@see struct nand_read_options)
 * @return      0 in case of success
 *
 */
int nand_read_opts(nand_info_t *meminfo, const nand_read_options_t *opts)
{
    int imglen = opts->length;
    int pagelen;
    int baderaseblock;
    int blockstart = -1;
    int percent_complete = -1;
    loff_t offs;
    size_t readlen;
    ulong mtdoffset = opts->offset;
    u_char *buffer = opts->buffer;
    int result;
    struct nand_oobinfo old_oobinfo;
    int oobinfochanged = 0;

    /* make sure device page sizes are valid */
    if (!(meminfo->oobsize == 16 && meminfo->oobblock == 512)
        && !(meminfo->oobsize == 8 && meminfo->oobblock == 256)
        && !(meminfo->oobsize == 64 && meminfo->oobblock == 2048)) {
        printf("Unknown flash (not normal NAND)\n");
        return -1;
    }

    pagelen = meminfo->oobblock
        + ((opts->readoob != 0) ? meminfo->oobsize : 0);

    /* check, if length is not larger than device */
    if (((imglen / pagelen) * meminfo->oobblock)
         > (meminfo->size - opts->offset)) {
        printf("Image %d bytes, NAND page %d bytes, "
               "OOB area %u bytes, device size %u bytes\n",
               imglen, pagelen, meminfo->oobblock, meminfo->size);
        printf("Input block is larger than device\n");
        return -1;
    }

    if (!opts->quiet)
        printf("\n");

    /* read the current oob info */
    memcpy(&old_oobinfo, &meminfo->oobinfo, sizeof(old_oobinfo));

    /* write without ecc? */
    if (opts->noecc) {
        memcpy(&meminfo->oobinfo, &none_oobinfo,
               sizeof(meminfo->oobinfo));
        oobinfochanged = 1;
    }

    /* get data from input and write to the device */
    while (imglen && (mtdoffset < meminfo->size)) {

        WATCHDOG_RESET ();

        /*
         * new eraseblock, check for bad block(s). Stay in the
         * loop to be sure if the offset changes because of
         * a bad block, that the next block that will be
         * written to is also checked. Thus avoiding errors if
         * the block(s) after the skipped block(s) is also bad
         * (number of blocks depending on the blockalign
         */
        while (blockstart != (mtdoffset & (~meminfo->erasesize+1))) {
            blockstart = mtdoffset & (~meminfo->erasesize+1);
            offs = blockstart;
            baderaseblock = 0;

            /* check all the blocks in an erase block for
             * bad blocks */
            if (!opts->nocheckbadblk) {
                do {
                    int ret = meminfo->block_isbad(meminfo, offs);

                    if (ret < 0) {
                        printf("Bad block check failed\n");
                        goto restoreoob;
                    }
                    if (ret == 1) {
                        baderaseblock = 1;
                        if (!opts->quiet)
                            printf("\rBad block at 0x%lx "
                                   "in erase block from "
                                   "0x%x will be skipped\n",
                                   (long) offs,
                                   blockstart);
                    }

                    if (baderaseblock) {
                        mtdoffset = blockstart
                            + meminfo->erasesize;
                    }
                    offs +=  meminfo->erasesize;

                } while (offs < blockstart + meminfo->erasesize);
            }
        }


        /* read page data to memory buffer */
        result = meminfo->read(meminfo,
                       mtdoffset,
                       meminfo->oobblock,
                       &readlen,
                       (unsigned char *) &data_buf);

        if (result != 0) {
            printf("reading NAND page at offset 0x%lx failed\n",
                   mtdoffset);
            goto restoreoob;
        }

        if (imglen < readlen) {
            readlen = imglen;
        }

        memcpy(buffer, data_buf, readlen);
        buffer += readlen;
        imglen -= readlen;

        if (opts->readoob) {
            result = meminfo->read_oob(meminfo,
                           mtdoffset,
                           meminfo->oobsize,
                           &readlen,
                           (unsigned char *)
                           &oob_buf);

            if (result != 0) {
                printf("\nMTD readoob failure: %d\n",
                       result);
                goto restoreoob;
            }


            if (imglen < readlen) {
                readlen = imglen;
            }

            memcpy(buffer, oob_buf, readlen);

            buffer += readlen;
            imglen -= readlen;
        }

        if (!opts->quiet) {
            int percent = (int)
                ((unsigned long long)
                 (opts->length-imglen) * 100
                 / opts->length);
            /* output progress message only at whole percent
             * steps to reduce the number of messages printed
             * on (slow) serial consoles
             */
            if (percent != percent_complete) {
            if (!opts->quiet)
                printf("\rReading data from 0x%x "
                       "-- %3d%% complete.",
                       mtdoffset, percent);
                percent_complete = percent;
            }
        }

        mtdoffset += meminfo->oobblock;
    }

    if (!opts->quiet)
        printf("\n");

restoreoob:
    if (oobinfochanged) {
        memcpy(&meminfo->oobinfo, &old_oobinfo,
               sizeof(meminfo->oobinfo));
    }

    if (imglen > 0) {
        printf("Could not read entire image due to bad blocks\n");
        return -1;
    }

    /* return happy */
    return 0;
}

/******************************************************************************
 * Support for locking / unlocking operations of some NAND devices
 *****************************************************************************/

#define NAND_CMD_LOCK       0x2a
#define NAND_CMD_LOCK_TIGHT 0x2c
#define NAND_CMD_UNLOCK1    0x23
#define NAND_CMD_UNLOCK2    0x24
#define NAND_CMD_LOCK_STATUS    0x7a

/**
 * nand_lock: Set all pages of NAND flash chip to the LOCK or LOCK-TIGHT
 *        state
 *
 * @param meminfo   nand mtd instance
 * @param tight     bring device in lock tight mode
 *
 * @return      0 on success, -1 in case of error
 *
 * The lock / lock-tight command only applies to the whole chip. To get some
 * parts of the chip lock and others unlocked use the following sequence:
 *
 * - Lock all pages of the chip using nand_lock(mtd, 0) (or the lockpre pin)
 * - Call nand_unlock() once for each consecutive area to be unlocked
 * - If desired: Bring the chip to the lock-tight state using nand_lock(mtd, 1)
 *
 *   If the device is in lock-tight state software can't change the
 *   current active lock/unlock state of all pages. nand_lock() / nand_unlock()
 *   calls will fail. It is only posible to leave lock-tight state by
 *   an hardware signal (low pulse on _WP pin) or by power down.
 */
int nand_lock(nand_info_t *meminfo, int tight)
{
    int ret = 0;
    int status;
    struct nand_chip *this = meminfo->priv;

    /* select the NAND device */
    this->select_chip(meminfo, 0);

    this->cmdfunc(meminfo,
              (tight ? NAND_CMD_LOCK_TIGHT : NAND_CMD_LOCK),
              -1, -1);

    /* call wait ready function */
    status = this->waitfunc(meminfo, this, FL_WRITING);

    /* see if device thinks it succeeded */
    if (status & 0x01) {
        ret = -1;
    }

    /* de-select the NAND device */
    this->select_chip(meminfo, -1);
    return ret;
}

/**
 * nand_get_lock_status: - query current lock state from one page of NAND
 *             flash
 *
 * @param meminfo   nand mtd instance
 * @param offset    page address to query (muss be page aligned!)
 *
 * @return      -1 in case of error
 *          >0 lock status:
 *            bitfield with the following combinations:
 *            NAND_LOCK_STATUS_TIGHT: page in tight state
 *            NAND_LOCK_STATUS_LOCK:  page locked
 *            NAND_LOCK_STATUS_UNLOCK: page unlocked
 *
 */
int nand_get_lock_status(nand_info_t *meminfo, ulong offset)
{
    int ret = 0;
    int chipnr;
    int page;
    struct nand_chip *this = meminfo->priv;

    /* select the NAND device */
    chipnr = (int)(offset >> this->chip_shift);
    this->select_chip(meminfo, chipnr);


    if ((offset & (meminfo->oobblock - 1)) != 0) {
        printf ("nand_get_lock_status: "
            "Start address must be beginning of "
            "nand page!\n");
        ret = -1;
        goto out;
    }

    /* check the Lock Status */
    page = (int)(offset >> this->page_shift);
    this->cmdfunc(meminfo, NAND_CMD_LOCK_STATUS, -1, page & this->pagemask);

    ret = this->read_byte(meminfo) & (NAND_LOCK_STATUS_TIGHT
                      | NAND_LOCK_STATUS_LOCK
                      | NAND_LOCK_STATUS_UNLOCK);

 out:
    /* de-select the NAND device */
    this->select_chip(meminfo, -1);
    return ret;
}

/**
 * nand_unlock: - Unlock area of NAND pages
 *        only one consecutive area can be unlocked at one time!
 *
 * @param meminfo   nand mtd instance
 * @param start     start byte address
 * @param length    number of bytes to unlock (must be a multiple of
 *          page size nand->oobblock)
 *
 * @return      0 on success, -1 in case of error
 */
int nand_unlock(nand_info_t *meminfo, ulong start, ulong length)
{
    int ret = 0;
    int chipnr;
    int status;
    int page;
    struct nand_chip *this = meminfo->priv;
    printf ("nand_unlock: start: %08x, length: %d!\n",
        (int)start, (int)length);

    /* select the NAND device */
    chipnr = (int)(start >> this->chip_shift);
    this->select_chip(meminfo, chipnr);

    /* check the WP bit */
    this->cmdfunc(meminfo, NAND_CMD_STATUS, -1, -1);
    if ((this->read_byte(meminfo) & 0x80) == 0) {
        printf ("nand_unlock: Device is write protected!\n");
        ret = -1;
        goto out;
    }

    if ((start & (meminfo->oobblock - 1)) != 0) {
        printf ("nand_unlock: Start address must be beginning of "
            "nand page!\n");
        ret = -1;
        goto out;
    }

    if (length == 0 || (length & (meminfo->oobblock - 1)) != 0) {
        printf ("nand_unlock: Length must be a multiple of nand page "
            "size!\n");
        ret = -1;
        goto out;
    }

    /* submit address of first page to unlock */
    page = (int)(start >> this->page_shift);
    this->cmdfunc(meminfo, NAND_CMD_UNLOCK1, -1, page & this->pagemask);

    /* submit ADDRESS of LAST page to unlock */
    page += (int)(length >> this->page_shift) - 1;
    this->cmdfunc(meminfo, NAND_CMD_UNLOCK2, -1, page & this->pagemask);

    /* call wait ready function */
    status = this->waitfunc(meminfo, this, FL_WRITING);
    /* see if device thinks it succeeded */
    if (status & 0x01) {
        /* there was an error */
        ret = -1;
        goto out;
    }

 out:
    /* de-select the NAND device */
    this->select_chip(meminfo, -1);
    return ret;
}

#endif /* (CONFIG_COMMANDS & CFG_CMD_NAND) && !defined(CFG_NAND_LEGACY) */
